Ask an Assam planter what is in the ground and you will usually get one of two answers: a clone, or old seed jat. This office has certified both. There is a third answer, less well known outside the trade, and it is not a compromise between the other two so much as a different tool built for a different job. It is called a biclonal seed variety, and Tocklai has been releasing them since the 1960s.

What a biclonal seed variety is, plainly

A clone is one plant, copied. Take a cutting from a single proven mother bush, root it, plant it out by the thousand, and every bush in that block carries that mother's exact genetic code. A seedling from old-style Assam jat is the opposite: open, uncontrolled pollination between an unknown mix of parents, so every bush in the field is a slightly different genetic draw.

A biclonal seed variety sits between those two, by design rather than accident. Breeders select two specific clones, already proven for traits they want (yield, drought tolerance, cup quality), and let them cross-pollinate under controlled conditions. The tea plant does not self-pollinate reliably, so a planned cross between two chosen parents reliably produces hybrid seed, the first, or F1, generation. That seed is then sold and planted as the biclonal variety. Cross three or more clones instead of two, and the result is called a polyclonal seed variety. The convention holds a name too: Tocklai's seed-derived lines carry the prefix TS, for Tocklai Seed, distinct from TV, for Tocklai Vegetative, the clone line this office has certified before.

Why breed a seed variety at all, once clones exist

The case for a biclonal variety is not nostalgia for the old seed gardens. It solves a specific problem clones cannot: a planted field of pure clone is one genotype end to end, which is efficient but fragile. A single pest, a single drought year, a single disease that happens to exploit that one genotype's weakness hits the entire block at once, because there is no genetic variation in the field to absorb it. Since a biclonal seed variety's parents are two different, deliberately chosen clones, the F1 seedlings it produces are not identical to each other. Each seedling draws a different combination of the two parents' genes, so a field planted from biclonal seed carries real variation again, while still descending from two known, proven parent lines rather than an unrecorded population.

That is the trade the old seed jat gardens could not offer with any precision: heterogeneity, yes, but from parents nobody had selected or measured. A biclonal seed variety keeps the resilience of variation and adds the part clonal breeding contributed, that both parents were chosen on purpose for known, useful traits.

The line Tocklai actually released

Tocklai's own published record puts the biclonal programme's rollout across five decades. The 1960s saw the first release, a biclonal seed stock bred under the "Nanda Devi" scheme for Darjeeling and recorded internally as Stock 378. The 1970s added three more, TS 397, TS 449, and TS 450. The 1980s brought TS 379, TS 462, TS 463, TS 464, and TS 491. The 2010s added a further seed stock for Darjeeling, TS 560, released alongside two new drought-tolerant clones, TTRI I and TTRI II, in the same round of releases.

By the count Tocklai and independent tea-research surveys give, the station has released 14 biclonal seed varieties and one polyclonal variety in total. The polyclonal, TS 203, crossed seven clones at once and was marketed under the name "Gaurisankar" for Darjeeling planting. It did not last: field performance across that many parent lines proved too unpredictable to recommend for commercial planting, and it was later withdrawn, which is itself the argument for stopping at two parents rather than seven. Only the biclonal line, with its two known, controlled parents, remained the standard recommendation for new plantings that want variation without gambling on an unrecorded cross.

What a garden actually gets from planting TS stock

The advantage is not abstract. TS 397, TS 449, and TS 450 remain among the most commonly cited biclonal stocks still referenced in Assam and Darjeeling planting guidance today, alongside newer releases like TS 506 and TS 589. Each carries the combined traits of its two named parent clones rather than the traits of one, so a planter choosing a biclonal stock is choosing a specific, documented cross, not an anonymous seedling. That is the same certification logic this office applies to a cup: know what went into it, and you can trust what comes out of it.

The tool exists elsewhere too, for the same reason. India's UPASI Tea Research Foundation runs its own biclonal line for South Indian gardens (BSS-1 through BSS-5), and Bangladesh's tea research institute has its own BTS series. Wherever a tea industry has both proven clones on hand and a reason to want variation back in the field, the biclonal cross is the tool reached for.

The one thing a biclonal variety does not give back

It is worth being plain about the limit. A biclonal seed variety restores variation, but only within the bounds of its two named parents. Cross any two proven TV clones and every resulting seedling is still some combination of those same two parents, drawing on the same narrow clonal gene pool this office has certified elsewhere, not the wide, uncatalogued pool a century of open-pollinated seed jat built up. Recovering that older pool is a different, slower project, the one a handful of estates such as Aideobarie have taken on directly. The biclonal seed variety is a narrower fix for a narrower problem: enough controlled variation in a new planting to stop one pest or one drought year from taking out an entire field at once, using parents the breeders already know and trust.

Sources

1. Clonal Seed Varieties, Tea World, Krishna Kanta Handiqui State Open University, on the definition of biclonal and polyclonal seed varieties, the TS naming line, and the withdrawal of the TS 203 polyclonal "Gaurisankar."
2. Achievements, Tea Research Association (Tocklai), on the decade-by-decade release record of biclonal seed stocks from Stock 378 in the 1960s through TS 560 in the 2010s.
3. Assam Jat, The Lost Seed, Rujani Tea, an interview with Dr S.K. Pathak, former Deputy Director of Tocklai, on the genetic narrowing that followed the industry-wide switch to clonal planting and the Aideobarie estate's separate effort to recover old Betjan seed jat.